A canine model was utilized to study and compare the effects of prostaglandins E1, A1, and F2α, theophylline, and cholera exotoxin upon net absorption or secretion of water and electrolytes from the jejunum. Superior mesenteric artery infusions of prostaglandins E1, A1, and F2α, and of theophylline each induced net secretion of water and electrolytes from the jejunum. Prostaglandin infusion into the jejunal lumen had a lesser effect upon net fluid movement than did prostaglandin infusion into the superior mesenteric artery at the same rates. Mucosal application of cholera exotoxin induced net secretion rates which exceeded the maximum net secretory rates induced by prostaglandin infusions. When theophylline and prostaglandin F2α were simultaneously infused into the superior mesenteric artery at low rates, significant synergism in the effect of these two agents on fluid movement was observed. There was a significant correlation between the magnitude of effect of intra-arterial prostaglandin and of intraluminal cholera exotoxin when determined in the same dog. The possible mechanisms by which these agents alter jejunal fluid movement are discussed and the possibility that they may act upon a single secretory mechanism is considered.
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